Living up to its name, the common blue damselfly is both very common and very blue. It is an insect which primarily inhabits freshwater habitats, such as slow flowing streams, lakes and regularly visits garden ponds. The male is pale blue with bands of black along the body; the female is either blue or dull green, with larger black markings along the body. Males often have a mushroom-shaped black marking just behind the thorax, whereas females have a thistle-shaped marking.
During mating, the male clasps the female by her neck while she bends her body around to his reproductive organs, forming what is called a ‘mating wheel’. The pair flies together over the water and eggs are laid within a suitable plant, just below the surface. The eggs hatch the following spring and the larvae, called nymphs, live in the water for a few years as an aquatic predator. When fully grown, the nymphs climb out of the water, up a suitable stem to moult into damselflies. Insect blood (haemolymph) is pumped into the wings and body to expand them. When the dragonfly is full size, they increase the temperature of the thorax by whirring the wings so the thorax can reach 27°C, at which point it can fly. It takes a few weeks of feeding and sunny weather before they are fully mature.
- Length: 32-35mm
- Wingspan: 40mm
The common blue damselfly is one of the most common damselflies found throughout the UK.
When to see
Best seen during the flight period between April and September. More common between May and August, especially on the Outer Hebrides.
- The common blue damselfly, like all damselflies and dragonflies has two huge compound eyes (30,000 individual facets). The eyes are so large, they take up most of the head, and 80% of the brain deals with visual information.
- Damselflies hold their wings together above their abdomens when at rest, whilst dragonflies on the other hand, have much broader abdomens and hold their wings out at right angles to their bodies when at rest.